Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
LinkedIn Premium - LinkedIn is a social network helping brands and professionals to connect, identify sales prospects, hire talent, and promote their business.
JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website
Salesforce Chatter - Salesforce Chatter provides a suite of collaboration features to any application built on Force.com.
tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page